A German citizen recruited by the KGB to spy for the Soviets in the 1980s, Hess broke into 400 U.S. military computers in order to obtain classified information, including the OPTIMIS Database at the Pentagon.

His activity was eventually detected by Clifford Stoll at the computer center of the Lawrence Berkeley Laboratory in California. Hess was found guilty of espionage and sentenced to one to three years in prison. Stoll wrote about the experience in a book titled “The Cuckoo's Egg.”

Cornell University graduate student Robert Morris just wanted to gauge the size of the Web in 1988, so he decided to create what would come to be known as the first worm on the Internet.

While Morris didn't intend the worm to cause any damage, a design flaw caused it to replicate itself at massively high levels, overloading systems and causing significant problems for administrators. Morris became the first person convicted under the Computer Fraud and Abuse Act in 1990 and was sentenced to three years of probation and community service.

Seen by many as one of the first high-profile instances of financially-motivated hacking, Russian crime-ring leader Vladimir Levin managed to gain access to accounts located in the Citibank network and stole millions of dollars in 1995.

As part of a larger crime group, Levin was able to get a list of customer codes and passwords that allowed him to log in and transfer $3.7 million illegally. The FBI eventually caught up with Levin, and he was sentenced to three years in jail in 1998. He was also ordered to pay Citibank $240,015 in restitution.

Known by the hacker name c0mrade, Jonathon James was 16 when, in 1999, he hacked into the Marshall Space Flight Center in Huntsville, Alabama, and downloaded proprietary software for the International Space Station.

NASA officials valued the documents stolen by James at around $1.7 million. The incident forced NASA to shut down its computer systems for three weeks and cost about $41,000 to fix.

In 2002, at age 19, Adrian Lamo hacked into the internal network of the New York Times and accessed many sensitive records, including an extensive database of op-ed writers the paper had used in the past. The record contained names and, in some instances, phone numbers, home addresses, and payment history on contributors such as Democratic strategist James Carville, former secretary of state James Baker, and (ironically, Sneakers movie veteran) actor Robert Redford.

Lamo added his own name to the list of “experts,” and under “expertise” he wrote "Computer hacking, national security, communications intelligence."

Scottish hacker Gary McKinnon, who went by the handle Solo, was accused of hacking into several U.S. military computers in 2001 and 2002. McKinnon allegedly wanted to know what the government knew about UFOs.

Military officials said the damage caused by McKinnon included the deletion of critical files from operating systems, prompting a shut down of the U.S. Army’s Military District of Washington network of 2,000 computers for 24 hours.

McKinnon is currently in London and has been fighting U.S. extradition orders for more than a decade.

Albert Gonzalez was the convicted ringleader of a group of cyber criminals that, from 2005 through 2007, stole more than 90 million credit and debit card numbers from TJX and other retailers, including shoe sellers DSW, OfficeMax, BJ’s Wholesale Club, and Dave & Busters. Gonzalez was also the mastermind behind the hacking that caused the massive records breach of Heartland Payment Systems in 2008.

In 2009, Gonzalez was sentenced to two concurrent 20-year prison sentences, the lengthiest sentence ever imposed in the United States for hacking or identity theft.

In early 2011, Antisec group Anonymous got angry when Aaron Barr, at the time the CEO of HB Gary Federal, alluded to plans to reveal the identities of several Anonymous members at the Security B-Sides conference.

In one of the first events to really bring “hacktivism” to the attention of the mainstream press, Anonymous retaliated by compromising the systems of both HBGary Federal and sister firm HB Gary Inc. Anonymous then copied and made public thousands of private HBGary documents, including emails.

Since the incident, Anonymous has made headlines with many more hacktivist attacks.

An offshoot of Anonymous, hacktivist group Lulzsec in June 2011 hacked into Sony Pictures via SQL Injection attack and stole data that included names, passwords, email, and home addresses of thousands of customers.

Lulzsec, saying the attack was retaliation for Sony's legal action against hacker George Hotz for jailbreaking the PlayStation 3, claimed to have compromised more than one million accounts. Sony has claimed the number of compromised accounts was much lower.

Lulzsec has since been associated with several other statement-making attacks. Founding Lulzec member Sabu (real name Hector Xavier Monsegur) was arrested by federal agents in June 2011 and eventually plead guilty to criminal charges, including multiple counts of conspiracy to engage in computer hacking.

Employees of British paper News of the World were found to have hacked into the phones of celebrities, politicians, and even murder victims in pursuit of stories for the tabloid.

In an investigation that dated back to 2002, it was eventually revealed that reporters, as well as private investigators hired by the paper, had hacked into the voicemail accounts of celebrities like model Elle McPherson and actress Sienna Miller, as well as members of the British Royal Family. The 168-year-old paper was eventually shuttered in the wake of the scandal.